Abstract:

The post-occipital sinus of the spinal vein is often used for the collection of blood samples
from crocodilians. Although this sampling method has been reported for several crocodilian
species, the technique and associated anatomy has not been described in detail in any
crocodilian, including the Nile crocodile (Crocodylus niloticus). The anatomy of the cranial neck
region was investigated macroscopically, microscopically, radiographically and by means of
computed tomography. Latex was injected into the spinal vein and spinal venous sinus of
crocodiles to visualise the regional vasculature. The spinal vein ran within the vertebral canal,
dorsal to and closely associated with the spinal cord and changed into a venous sinus cranially
in the post-occipital region. For blood collection, the spinal venous sinus was accessed
through the interarcuate space between the atlas and axis (C1 and C2) by inserting a needle
angled just off the perpendicular in the midline through the craniodorsal cervical skin, just
cranial to the cranial borders of the first cervical osteoderms. The most convenient method
of blood collection was with a syringe and hypodermic needle. In addition, the suitability
of the spinal venous sinus for intravenous injections and infusions in live crocodiles was
evaluated. The internal diameter of the commercial human epidural catheters used during
these investigations was relatively small, resulting in very slow infusion rates. Care should be
taken not to puncture the spinal cord or to lacerate the blood vessel wall using this route for
blood collection or intravenous infusions.